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Assembly Source File | 1993-05-10 | 14.7 KB | 270 lines

; Program FSecret ( Chapter 11 ) ; page 55,132 ; ; This program installs additional handlers for interrupt 13h ; ; New function 0EFh of interrupt 13h has been added. ; This function has 3 subfunctions: ; 00 - installation check ; 01 - activates the driver ; 02 - deactivates the driver ; 03 - report the driver state; returns the state in AH (1 - on, 2 - off) ; To call new function put its number into the AH register, ; the subfunction number into AL and call interrupt 13h ; NewFunc equ 0E0h CheckIn equ 0 ; subfunction "check installation" IdSwOn equ 1 ; subfunction "turn program on" IdSwOff equ 2 ; subfunction "turn program off" RepSt equ 3 ; subfunction "report status" IdUnIn equ 4 ; subfunction "get resident PSP address" InAct equ 0 ; this value indicates "INACTIVE" Act equ 13h ; this value indicates "ACTIVE" _Text segment para public 'CODE' assume cs:_Text ;==================== Resident data ===================================== ActInd db Act ; activity indicator; if 0 - inactive ResPSP dw ? ; addres of resident PSP ResOff dw ? ; offset of resident part ResSeg dw ? ; segment of resident part ;===================== Resident code ==================================== Handler proc near ; additional handler for interrupt 13h pushf cmp ah,NewFunc ; additional function of INT 13h? je Addf ; new handler for that function cmp ActInd,Act ; is activity indicator set? jne ToOld13 ; if so, continue work ;=== Check whether the screen is already blanked Process:cmp dl,79h ; Is the floppy disk requested? ja ToOld13 ; If not, jump to the old handler cmp ah,03h ; Function 03 - write sector je RepCod ; new handler for function 03 cmp ah,0Bh ; Function 0B - write long sector je RepCod ; new handler for function 0Bh jmp ToOld13 ; Others processed by old handler ;=== Process write commands RepCod: cmp ActInd,Act ; Is the active mode set? jne ToOld13 ; If not, jump to the olf handler mov ah,04h ; Function 04h - verify sector ;=== Pass the control to the standard handler of the interrupt 13h ToOld13:popf db 0EAh ; this is code for JMP FAR OldOff dw 0 ; here will be ofsset OldSeg dw 0 ; here will be segment ;=== Process additional function of interrupt 13h Addf: cmp al,CheckIn ; is installation check required? je Inst cmp al,IdSwOn ; turn driver ON? je SwOn cmp al,IdSwOff ; turn driver OFF? je SwOff cmp al,RepSt ; report status? je Report cmp al,IdUnIn je RetPSP jmp ToOld13 ; unknown command - pass to old handler Inst: mov ah,CheckIn ; value to be returned into AH jmp ExHand ; exit handler SwOn: mov ActInd,Act ; set indicator to ACTIVE (ON) mov ah,IdSwOn ; value to be returned into AH jmp ExHand ; exit handler SwOff: mov ActInd,InACt ; set indicator to INACTIVE (OFF) mov ah,IdSwOff ; value to be returned into AH jmp ExHand ; exit handler RetPSP: mov ah,IdUnIn ; value to be returned into AX mov dx,ResPsp mov es:[bx+0],dx ; segment address of resident PSP mov dx,OldOff mov es:[bx+2],dx ; offset addres of old handler mov dx,OldSeg mov es:[bx+4],dx ; segment address of old handler mov dx,Resoff mov es:[bx+6],dx ; offset addres of this handler mov dx,ResSeg mov es:[bx+8],dx ; segment address of this handler jmp ExHand ; exit handler Report: mov ah,IdSwOff ; prepare "InActive" code for returning cmp ActInd,Act ; is activity indicator set? jne ExHand ; if not, exit handler mov ah,IdSwOn ; return "Active" code ExHand: mov al,NewFunc ; return additional signature in AL popf iret ; return from handler Handler endp ;=== Installation part of the program BegInst label byte ParmInd db 0 PspAddr dw ? ComSeg dw ? ResArea dw 5 dup (?) ; buufer for subfunction "return PSP" RetCode db 0 Start: mov PspAddr,es ; save address of PSP mov sp,0F000h ; set the stack ;=== Free the environment memory block mov es,es:[2Ch] ; address of environment block into ES mov ah,49h ; function 49h - free memory block int 21h ; DOS service call ;=== mov es,PspAddr ; set ES to point to PSP mov ComSeg,cs ; save current command segment mov ds,ComSeg ; DS = CS - data and code are the same ;=== check whether the program is alrady installed mov ah,NewFunc ; new funtion of INT 13h mov al,CheckIn ; AL - installation check int 13h ; call interrupt 13h - timer tick cmp ah,Checkin ; does AH contain function number? je Already ; if YES, handler is already installed ;=== output the initial message mov ah,09 ; function 09 - text string output lea dx,BegMsg ; DX - address of message int 21h ; DOS service call mov ResPSP,es ; save PSP of resident part ;=== modyfying IVT mov ax,3513h ; function 35h - Get Interrupt Vector int 21h ; DOS service call mov OldOff,bx ; save offsett of old handler for 13h mov OldSeg,es ; save segment of old handler for 13h mov ResOff,offset Handler ; save offset of resident part mov ResSeg,ds ; save segment odf resident part cli ; caution! critical part of program mov dx,ResOff ; address of handler mov ax,2513h ; function 25h - Set new handler int 21h ; DOS service call sti ; critical part finishes here ;=== output the message "program is installed" mov ActInd,Act ; set activity indicator (TSR "ON") lea dx,Loaded ; DX - address of message mov ah,09h ; function 09 - output string int 21h ; DOS service call ;=== calculate the size of the resident part lea dx,BegInst ; address of installation part beginning add dx,110h ; PSP length plus 16 byte (insurance) mov cx,4 ; set counter for shift shr dx,cl ; 4 bits to the right - divide by 16 mov ax,3100h ; 31h - terminate and state resident int 21h ; DOS service call ;=== Normal exit from program (return code 0) NormEx: mov ds,ComSeg ; restore DS (can be destroyed) mov ah,09h ; function 09 - output string int 21h ; DOS service call mov ah,4Ch ; function 4Ch - terminate process mov RetCode,al ; return code into AL int 21h ; DOS service call ;=== Process situation "Resident part is already installed" Already:mov es,PspAddr ; addres of PSP into ES cmp byte ptr es:[80h],1 ; are there parameters? jle NoParm ; if not, set the indicator "NoParm" mov bx,82h ; BX - beginning of parameter string cmp byte ptr es:[bx],'/' jne CheckS SkipSep:inc bx jmp ChkLtr CheckS: cmp byte ptr es:[bx],'-' je SkipSep ChkLtr: cmp byte ptr es:[bx],'?' je Help and byte ptr es:[bx],0DFh ; force first letter uppercase cmp byte ptr es:[bx],'H' ; is first letter 'H'? je Help ; if so, process "HELP" cmp byte ptr es:[bx],'U' ; is first letter 'U'? je UnInst ; if so, process "UNINSTALL" cmp byte ptr es:[bx],'O' ; is first letter 'O'? jne InvParm ; if not - missing or invalid and byte ptr es:[bx+1],0DFh ; force second letter uppercase cmp byte ptr es:[bx+1],'N' ; is second letter 'N'? je TurnOn ; if so, process "ON" cmp byte ptr es:[bx+1],'F' ; is second letter 'F'? jne InvParm ; if not - invalid parameter and byte ptr es:[bx+2],0DFh ; force third letter uppercase cmp byte ptr es:[bx+2],'F' ; is third letter 'F'? jne InvParm ; if not, process "INVALID PARMS" mov al,IdSwOff ; code for subfunction "OFF" into AL jmp Switch ; switch program state ;=== deinstall new handler Uninst: mov ah,NewFunc ; AH - code for additional function ;--- get information about the resident part (PSP, segment, offset) mov al,IdUnIn ; AL - subfunction "deinstallation" mov es,ComSeg ; ES points to current segment mov bx,offset ResArea ; ES:BX - buffer for subf. "Return PSP" ;--- get information about current handler of interrupt 13 int 13h ; call new handler of interrupt 13h mov ax,3513h ; function 35h - get interrupt vector int 21h ; DOS service call ;--- is the resident part of this program last handler of interrupt 13h? mov ax,es ; AX - segment of current handler cmp ax,ResArea[8] ; segment of resident part jne Over ; if not equal - res. part overriden cmp bx,ResArea[6] ; compare offsets jne Over ; if not equal - res. part overriden ;--- free memory occupied be the resident part of TSR mov es,ResArea[0] ; address of resident PSP into ES mov ah,49h ; function 49h - free memory block int 21h ; DOS service call ;--- make previous handler of interrupt 13 current mov ds,ResArea[4] ; DS - segment of old handler mov dx,ResArea[2] ; dx - offset of old handler mov ax,2513h ; function 25h - set interrupt vector int 21h ; DOS service call mov ds,ComSeg ; restore data segment register ;--- leave program lea dx,UnInMsg ; DS:DX - point to message "uninstalled" jmp NormEx ; leave program ;--- process situation "TSR overriden" Over: lea dx,OverMsg ; DS:DX - point to message "overriden" jmp NormEx ; leave program ;=== Turn the program ON TurnOn: mov al,IdSwOn ; subfunction "Turn ON" ;=== This block switches program state Switch: mov ah,NewFunc ; AH - code for additional function int 13h ; call new handler of interrupt 13h ;=== Process the situation "no parameter" NoParm: mov ah,NewFunc ; AH - code for additional function mov al,RepSt ; AL - subfunction "Report Status" int 13h ; call new handler of interrupt 13h lea dx,MakeOff ; DS:DX - addres of message "Turned OFF" cmp ah,IdSwOn ; is code "Turned ON" returned? jne FinTst ; if not, exit; "OFF" will be output lea dx,MakeOn ; DS:DX - addres of message "Turned ON" FinTst: jmp NormEx ; to print message and exit ;=== Output help message Help: lea dx,BegMsg ; DS:DX - address of initial message Help2: mov ah,09h ; function 09 - output text string int 21h ; DOS service call lea dx,ParmTxt ; DS:DX - address of HELP message jmp NormEx ; to print message and exit ;=== Process the sitution "INVALID PARAMETERS" InvParm:lea dx,Invalid ; DS:DX addres of message "Invalid" mov RetCode,1 ; return code = 1 jmp Help2 ; to print message and exit ;=== Data for non-resident part of the program CR equ 0Ah LF equ 0Dh EndMsg equ 24h Invalid db CR,LF,'Can not interprete parameters specified.' db CR,LF,'The valid form of command line is:',CR,LF,EndMsg BegMsg db CR,LF,'The floppy disk security system version 2.5 29.07.92' db CR,LF,'Copyright (C) 1992 V.B.Maljugin, Russia, Voronezh' CRLF db CR,LF,EndMsg Loaded db CR,LF,'Program is installed successfully',CR,LF,EndMsg MakeOn db CR,LF,'The floppy disk guard is now ACTIVE',CR,LF,EndMsg MakeOff db CR,LF,'The floppy disk guard is now INACTIVE',CR,LF,EndMsg HelpTxt db CR,LF,CR,LF, 'Call: ' ParmTxt db CR,LF,'FSecret [on | off | u | /? | /h | -? | -h] ',CR,LF db CR,LF,'Parameters: ' db CR,LF,'on - make the floppy disk guard active ' db CR,LF,'off - make the floppy disk guard inactive ' db CR,LF,'u - uninstall the floppy disk guard; FSecret must be' db CR,LF,' the last handler for interrupt 13h' db CR,LF,'rest of list - output this text.',CR,LF db CR,LF,'First call of the program always means installation.' db CR,LF,'Call this program without parameters to determine its ' db 'current state.', CR,LF,EndMsg OverMsg db CR,LF,'Program FSecret is not last handler of interrupt 13h.' db CR,LF,'Deinstallation denied. Please deinstall program manually' db CR,LF,EndMsg UnInMsg db CR,LF,'Program FSecret uninstalled.',EndMsg _text ends end Start